1. Field of the Invention
The present invention relates to a thin-film magnetic head with a heating element, a head gimbal assembly (HGA) with the thin-film magnetic head and a magnetic disk drive apparatus with the HGA, and to a method for controlling a magnetic spacing during writing data in the magnetic disk drive apparatus.
2. Description of the Related Art
In a magnetic disk drive apparatus, when writing or reading signals, a thin-film magnetic head hydrodynamically flies with a predetermined spacing (flying height) on a rotating magnetic disk. While flying on the magnetic disk, the thin-film magnetic head writes signals to the magnetic disk using magnetic fields generated from an inductive write head element, and reads signals by sensing magnetic fields corresponding to the signals from the magnetic disk with use of an magnetoresistive (MR) effect read head element. On these cases, a magnetic spacing dMS is defined as the effective magnetic distance between ends of these magnetic head elements and the surface of the magnetic disk.
With higher recording density due to the increasing data storage capacity and the miniaturization of the magnetic disk drive apparatus in recent years, a track width of the thin-film magnetic head is becoming smaller. In order to avoid the degradation of the writing and reading performance due to the smaller track width, latest magnetic disk drive apparatuses actually have the magnetic spacing dMS reduced down to the order of 10 nm. In the case, some techniques are proposed, which controls the smaller the dMS with some accuracy by positively utilizing a thermal pole tip protrusion (TPTP) phenomenon with the use of a heater provided near or inside the magnetic head element, for example, in U.S. Pat. No. 5,991,113, US Patent Publications Nos. 2003/0174430 A1 and 2003/0099054 A1, and Japanese Patent Publication No. 05-020635A.
However, in the thin-film magnetic head with the above-mentioned heater, a problem has been occurring, which the deficiency in the writing performance during the starting period of writing can not be adequately dealt with.
The TPTP phenomenon is inherent in the inductive write head element that is protruded toward the magnetic disk surface by thermal expansion due to a Joule heat and an eddy-current loss heat. In the inherent case, this protrusion begins as soon as writing, and the magnetic spacing dMS decreases during a predetermined period, then, settles down to a predetermined value. That is to say, during this predetermined period, because the magnetic spacing dMS is larger than this predetermined value, the writing performance becomes deficient. Therefore, in the front region of the sector that signals were written under the deficient writing performance, a reading error is likely to occur. Even if the heater described in the above-mentioned U.S. patent documents is used to protrude the write head element prior to writing, an enough protrusion can not be generated timely at the start of writing because the response of the protrusion due to the heat generated from the heater is rather slow.
Meanwhile, by using the thin-film resistor described in Japanese Patent Publication No. 05-020635A, which is formed between the upper and lower magnetic pole layers as well as the thin-film coil is, the protrusion response due to the heat generated from the thin-film resistor can be set to the same level as that due to the heat generated from the thin-film coil. In the case, however, a magnetic flux induced by the current flowing through the thin-film resistor reaches the magnetic disk surface via the magnetic pole layers, and causes an unwanted writing. By the unwanted writing, a writing error is likely to occur during the starting period of writing.